This invention relates to improvements to an accelerator pump for a carburetor.
The accelerator pump for the carburetor is provided for obtaining a substantial acceleration of fuel supplied into a main fuel supplying system of the carburetor during acceleration. This accelerator pump comprises a cylinder formed in a carburetor body, a piston assembly slidably inserted in the cylinder, and a link mechanism connected to a throttle valve for actuating the piston assembly. An amount of fuel supplied during acceleration is determined by a stroke of the piston assembly made by movement of the link mechanism during acceleration, therefore, it is necessary to adjust the stroke precisely. When an excess amount of fuel is supplied the acceleration is increased, but, an amount of CO in the exhaust gas increases. If a user deforms the link mechanism to provide a larger stroke in order to obtain greater acceleration beyond that achievable with factory settings, there will be produced an increase in the amount of harmfull components in the exhaust gas. Re-adjustments by the user which would increase the stroke of the piston must be prevented if environmental exhaust gas requirements are to be met. Therefore, some measurement of preventing such a readjustment has been desired.
On the other hand, in Japanese patent publication No. 4801/1975 disclosed in an accelerator pump which is provided with a stopper 7 provided on a heat sensitive liquid 8 contained in a cavity formed in a lower portion of a pump chamber for keeping a quantity of fuel supplied during acceleration constant irrespectively of temperature changing. In this accelerator pump, it is apparent that a stroke of an accelerating piston 6 can be changed by deformation of a link mechanism (not shown) because elevation of the accelerating piston 6 is determined by the link mechanism. Therefore, even if such a stopper 7 is provided, any kind of stroke can be obtained by deforming the link mechanism.